While I love the idea of free and open software, I have to admit an ignorance to it in application (well, at least Linux). Valve creates a Steam client, and ge

While I love the idea of free and open software, I have to admit an ignorance to it in application (well, at least Linux). Valve creates a Steam client, and gets the Source game engine running awesomely on "Linux". How do all the different desktops factor into this?